Seeking Better Cancer Screenings
What if doctors could screen for multiple forms of cancer in just one comprehensive test, the way computer software screens a hard drive for viruses?
Johns Hopkins cancer researcher Nickolas Papadopoulos and his team have developed a cancer detection tool that accomplishes something similar: It screens for eight common cancers—five of which previously had no screening test—through one simple blood draw. “Even with new therapeutics and new drugs, it turns out it’s still very hard to treat people with advanced cancer,” Papadopoulos says. “Finding the cancers early is going to be something that has a great potential of changing the number of deaths.”
Previously, researchers had proved that malignant tumor cells shed DNA—just one or two pieces of which join the tens of thousands of DNA strands from healthy cells floating in the bloodstream. Theoretically, finding those mutated pieces of DNA could help doctors detect cancer significantly earlier than other screenings, but doing so was like looking for a needle in a haystack, Papadopoulos says. Screening technologies just weren’t sensitive enough to pick up the tiny warning signals, but recent advancements proved the theory could work—at least in patients with advanced cancers, as Papadopoulos discovered in another study.
But the oncologist wanted to take the test a step further by devising a way to spot cancer at its earliest stages. This time, researchers tested blood samples for two markers: the tiny pieces of DNA shed by nascent tumors—the needles in the haystack—and specific proteins that are known to be elevated in people who have cancer.
By searching for that combination of genes and proteins, the researchers proved their test, which they dubbed CancerSEEK, could successfully identify cancers of the breast, ovary, lung, liver, pancreas, esophagus, colorectum, and stomach—all from a single blood draw. It also turned out to be promisingly accurate: Across cancer types, the median ability to detect the disease was 70 percent—ranging from a low of 33 percent sensitivity for breast cancer to 98 percent sensitivity for ovarian cancer. Practically, it means diagnosing cancer in its earliest stages, long before symptoms start showing up.
However, the test can only find cancers that leave enough DNA traces for current blood-screening technologies to pick up. For example, in previous research, Papadopoulos found that blood tests are still unable to pick up the presence of brain tumors—the DNA just isn’t detectable, he explains. This could be because these tumors shed fewer pieces of mutated DNA or that modern technology still isn’t sensitive enough to detect them. It may also be that DNA from these tumors is blocked from entering the bloodstream. “We blame this on the blood-brain barrier,” Papadopoulos says.
CancerSEEK is currently in larger clinical trials to further validate its cancer-finding claims and to determine how often and at what age doctors should start offering the test. Whether CancerSEEK will one day be included in the regimen of tests at annual physicals remains to be seen, but it marks an important stride in the way cancer will be detected and ultimately cured, Papadopoulos says. “This is something that potentially can save a lot of lives.”